摘要:

The hypothesis, that through use of a host, a hemiparasitic angiosperm will be able to “uncouple” physiological functions from microenvironmental variations, was tested by field measurements of water and carbohydrate balance betweenCastilleja chromosaand hostArtemisia tridentatain three different microhabitats in the White Mountains of California. Movement of reducing sugars from host to parasite correlated with the water potential gradient from host to parasite, and the gradient occurred when water potentials of the host‐parasite system exceeded 15 bars. Changes in carbohydrate and water balance inCastillejawere unaffected by microclimatic differences, whereas these same functions in the host were tightly coupled with differences in microhabitat.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06249.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

The duration of mitosis and the cell cycle were determined for defined cell populations of the shoot apical meristem ofCeratopteris thalictroidesBrong. by using the colchicine‐induced metaphase accumulation technique. The results indicate that the apical cell is mitotically active and cycles at an apparently greater frequency than the cells of subjacent populations. Duration of mitosis was similar for all cells of the meristem. These results are correlated with mitotic indices of control apices, the geometry of the apex, and the mean number of cells in the meristem. Shoot apices from adult plants were examined to determine mitotic indices within the meristem; mitotic activity was again noted for the apical cell. These results contradict recent proposals that the pteridophyte apical cell serves as a unicellular quiescent center which lacks histogenic potential and offer experimental support for the classical concept of apical cell function in those fern shoot meristems which terminate in a single apical cell.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06250.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

This study comparesHerissantia tiubaewith 10 species ofGayaH.B.K., andHerissantiaMedicus. The pollen morphology of the eleven species is described in detail by observations from both the scanning electron and light microscopes. The palynological data were used to produce pollen descriptions and a phenogram based on similarity coefficients. This information was combined with morphological and cytological data to determine the taxonomic relationship and proper placement ofH. tiubae, which has the pollen characteristics ofHerissantiaand is properly placed in that genus.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06251.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Heartwood flavonoids of 23 taxa ofRhusL. were surveyed in order to assess infrageneric relationships and classification. Fourteen flavonoids and two coumarins were detected in the heartwood extracts. All taxa were characterized by a flavonoid complement consisting of eight 5‐deoxyflavonoids involving several aglycone classes (e.g., flavonols, flavones, aurones, chalcones and dihydroflavonols) and the aurone rengasin. None of the 5‐hydroxyl analogs of the 5‐deoxyflavonoids were detected in the heartwood extracts. Infraspecific flavonoid patterns were uniform in different populations, although the presence of 3′,4′‐dihydroxyflavone 4′‐O‐β‐glucoside varied in some taxa. Taxa ofRhussubgenusRhusconsistently differed from all taxa ofRhussubgenusLobadiumin lacking glycosides of fisetin, butein and 3′,4′‐dihydroxyflavone. The major evolutionary trend in the heartwood flavonoids ofRhusappears to be accumulation of simple mono‐ or diglucosides. Data from heartwood flavonoids suggest thatRhusbe treated as consisting of two subgenera (RhusandLobadium) and that subgenusLobadiumbe divided into three sections.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06252.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

The phloem ofEtapteris leclercqiiandBotryopteris tridentatapetioles is described from Lower Pennsylvanian coal balls. Petioles ofB. tridentataare characterized in transverse section by an omega‐shaped xylem trace, a phloem zone which extends from 2‐10 cells in width, and 2‐parted cortex.Etapteris leclercqiipetioles exhibit a 4–9 cell‐wide phloem zone surrounding the central clepsydroid xylem mass, and a 3‐parted cortex. In both taxa a 1–2 cell layer parenchyma sheath separates the xylem from the extra‐xylary tissues. The phloem of both species consists of sieve elements that average about 20 μm in diam by 200 μm in length inBotryopteris, and 100 μm in length inEtapteris, with horizontal‐slightly oblique end walls. In transmitted light, the radial walls of the sieve elements form an irregular reticulate pattern enclosing elliptical lighter areas. With the scanning electron microscope, these areas appear as horizontal‐slightly oblique furrows on the cell wall, with many small indentations lining the furrows. These indentations, because of their regular occurrence and size (from a few fractions of a micron up to 1.0 μm in diam), are interpreted as sieve pores, and the elliptical areas that enclose them as sieve areas. The phloem ofE. leclercqiiandB. tridentatais compared with that described for other fossil genera and with that of extant ferns.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06253.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

The contractile roots of the horticultural varietyFreesia hybridaBailey (Iridaceae) were determined to contract via a growth/collapse mechanism. Contraction is initiated by a radial growth of middle and outer cortical parenchyma cells which is morphologically evident by an expanded diameter of the root. No concomitant decrease in length of the actively growing cells was observed. Shortening of the root is caused by axial tension produced by the radial growth of cells contiguous with nonexpanded cells distally. Centripetal collapse of expanded cells, coupled with passive shortening of inner cortical parenchyma and stelar tissues, releases axial tension slowly, returning the shortened root to equilibrium. Inner cortical parenchyma cells shorten in an accordion‐like manner facilitated by partial dissolution of middle lamellar material.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06254.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

A single application of gibberellic acid to young internodes significantly accelerated the rate of internode growth and the rate of leaf production in shoots ofXanthium pennsylvanicumWallr. The average duration of one plastochron in treated plants was reduced to 43% of control levels. Gibberellic acid also had a pronounced morphogenetic effect on leaves so that the area and leaf length of treated plants were both significantly reduced. Depending upon concentration, auxin had both inhibitory and promotive effects onXanthiumshoots. Indole‐3‐acetic acid markedly altered the response of the gibberellic acid‐treated internodes and those located above and below the site of application. In addition, high auxin concentrations induced the formation of adventitious roots in treated internodes. Auxin also brought about significant reductions in the length and area of leaves developed under the influence of this hormone.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06255.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

A morphometric approach proved useful for characterizing pollen from theAmbrosiaspecies that are responsible for most ragweed hayfever and for correctly identifying individual pollen grains. Pollen was harvested from 4 species (A. trifida, A. artemisiifolia, A. bidentata, A. psilostachya) grown in Champaign County, Illinois, and observed with a scanning electron microscope. Quantitative measurements of 6 different exine characters were made on micrographs of 96 pollen grains from each species. Discriminant analysis based on these characters was used to obtain a population centroid for each species and indicated that these centroids were distinctly different. This analysis also included a species classification for individual pollen grains and indicated probability of species membership. About 86% of all individuals were correctly classified when the 4 species were included, with a range from 80% (A.artemisiifolia) to 95% (A. psilostachya). When three species (A. trifida, A. artemisiifolia, A. bidentata) were analyzed, about 87% of the individuals were correctly classified, and almost all individuals (97%) were classified correctly when onlyA. trifidaandA. artemisiifoliawere included. The validity of the derived discriminant functions was also tested by treating herbarium specimens as unknowns. The species and percentages of these individuals correctly classified wereA. trifida(100%),A. artemisiifolia(58%),A. bidentata(100%), andA. psilostachya(31%). The classification results using three species wereA. trifida(100%),A. artemisiifolia(75%), andA. bidentata(100%); and using two species wereA. trifida(100%) andA. artemisiifolia(92%). Hence, the disciminant functions do seem valid for 3 species, but further investigation ofA. psilostachyais needed. This type of approach may be useful in pollen analysis, especially where these species significantly contributed to aeroallergens.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06256.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Mature spores ofRiccia californica, R. campbelliana, R. sorocarpa, andR. trichocarpa(Marchantiales, Ricciaceae) were examined with both scanning and transmission electron microscopes. The thick‐walled spores have species‐specific surface sculpturing and similar internal structure. Major surface features include ridges and depressions in areolate or irregular configurations. Finer surface features such as tubercles or papillae may ornament the ridges or depressions. Internally, the sporoderm consists of a thin intine and a three‐layered, lamellate exine. The innermost exine lamellae are thin and closely spaced, giving this layer a fibrillar appearance. Lamellae of the middle region are thick in section and have a relatively thick, electron‐dense coating. The outermost lamellae are of intermediate thickness and also have a relatively thick electron‐dense coating. Lamellae of all regions frequently split, branch and anastomose. The outermost lamella forms the surface features of the spore. Interior lamellae follow the contour of the outermost lamella. Pores usually occur in these four species at the junctures of the triradiate ridge arms and equatorial rim. Pores do not penetrate the entire exine, and they represent localized areas where the outermost group of lamellae have not been formed.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06257.x

出版商:Wiley    

年代:1979

数据来源: WILEY

摘要:

Growth ofRanunculusshoots through ontogeny is quantified by techniques utilizing scanning electron microscopy and studies on living plant material. The order of the contact parastichy phyllotaxy in the apical system is related to the relative plastochron rates of growth of the shoot. There is a change in the (2, 3) contact parastichy pattern of vegetative phyllotaxy to a transitional (3, 5) contact pattern which is maintained through sepal production. Formation of a 5(1, 1) whorl of petal primordia establishes a (5, 8) contact pattern with the sepal primordia. Subsequent initiation of stamen primordia, in spiral sequence, results in (5, 8, 13) triple contacts between petal and stamen primordia. The stamen primordia and carpel primordia arrangement is characterized by a (8, 13) contact parastichy pattern of phyllotaxy. Through ontogeny the volume of the shoot apex progressively increases but the shape of the apex, described by a second degree polynomial, remains constant. The plastochron and the relative plastochron rates of radial and vertical displacement of primordia progressively decrease during transition but there is no alteration of the chronological rate of apical expansion. The change in contact parastichy phyllotaxy through ontogeny is interpreted as a change in the relative positions of primordia insertion on the apex resulting from an increase in apical volume and an increased rate of primordia initiation.

ISSN:0002-9122    

DOI:10.1002/j.1537-2197.1979.tb06258.x

出版商:Wiley    

年代:1979

数据来源: WILEY